diff --git a/CMakeLists.txt b/CMakeLists.txt
index 302c08a..6a3d6ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -23,7 +23,7 @@ include(GNUInstallDirs)
 
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -pedantic -std=c99")
 if (${CMAKE_SYSTEM_NAME} MATCHES "Linux")
-  add_definitions("-D_XOPEN_SOURCE=600")
+  add_definitions("-D_GNU_SOURCE")
 else ()
   include_directories(AFTER SYSTEM "/usr/local/include")
   link_directories("/usr/local/lib")
diff --git a/src/sources/CMakeLists.txt b/src/sources/CMakeLists.txt
index 1912e0f..6063ebe 100644
--- a/src/sources/CMakeLists.txt
+++ b/src/sources/CMakeLists.txt
@@ -7,6 +7,9 @@ list(APPEND SOURCES "f2b_source_files")
 add_library("f2b_source_portknock" MODULE "portknock.c" "../strlcpy.c")
 list(APPEND SOURCES "f2b_source_portknock")
 
+add_library("f2b_source_mcast" MODULE "mcast.c" "../strlcpy.c")
+list(APPEND SOURCES "f2b_source_mcast")
+
 find_library(REDIS_FOUND "hiredis")
 if (WITH_REDIS AND REDIS_FOUND)
   add_library("f2b_source_redis" MODULE "redis.c" "../strlcpy.c")